Merc camp is located in EPF at 760,1380. It's located on island, connected to mainland by bridge. While you need to be on island inside camp while spawning them, killing mercs is usually conducted on mainland, just after bridge. Easier to manage adds.
Prior to start of raid someone must obtain Sealed Letter. you need to talk to ICC Commander inside ICC (center of Andromeda) and ask about Jack Two Fingers. He'll direct you to proper spawn place (you'll have 15 min to get there), where you'll talk to Jack. (Since I'm at work I'll have to check proper answers later).
Spawning Otacustes : inside camp at 720,1315 is Primus. He's placeholder for Ota. Respawn time is 15 min. 3 higher level chars can do the spawning, but also team of 150+ with some healing can do it. It's best if spawners face west, since primus tend to run when low on health (to prevent multiple adds).
Once Ota is spawned raid force should leave encampment and regroup at other side of bridge. Feeder trades in letter to Otacustes and Mercaniers spawn.
Pulling and killing : Puller can do his/her job safest with debuffs (with increased nano range..items+buffs). Should puller get agro from more than one merc, he should pull in different direction and get killed. If raidforce isn't competing for kill, it doesn't really matters how teams are set up. It's essential there's at least one good tank present and couple of docs. Docs should all have heal macro. Tank should solo pulled merc for some time to ensure agro don't flicker. After couple of minutes rest of raid force can join in, going easy with specials at start. Once done with one merc, puller can go for more.
Mercs have their different tricks, loot and range in difficulty. From easy to hard they go like : Nelly, Peter, Patricia, Ris, Ian. Ian has AoE nuke and stun. If not engaged, all still living merc respawn in 2 hours.